Vehicle locating unit with improved power management method

ABSTRACT

A method of checking messages from a network of communication sources includes initially testing the signal strength of a plurality of communication sources, storing the identity of the communication sources with the two strongest signals, and alternatively entering a sleep mode and a wake-up mode, the wake-up mode synchronized to the communication source with the strongest signal. The method further includes testing the signal strength of one additional communication source, switching synchronization to the additional communication source if said source presents a signal stronger than the signal of a stored communication source with the strongest signal, and replacing the identity of any stored communication source if an additional communication sources tested in sequence presents a signal stronger than the signal of said stored communication source.

RELATED APPLICATIONS

This application is a divisional of prior U.S. patent application Ser.No. 11/131,847 filed May 18, 2005, and claims the benefit of andpriority to U.S. patent application Ser. No. 11/131,847 which isincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to vehicle recovery systems and, in particular, avehicle locating unit of such a system with improved power managementtechniques.

BACKGROUND OF THE INVENTION

The applicant's successful and popular vehicle recovery system soldunder the trademark LoJack® includes a small electronic vehicle locatingunit (VLU) with a transponder hidden within a vehicle, a private networkof communication towers each with a remote transmitting unit (RTU), oneor more law enforcement vehicles equipped with a vehicle tracking unit(VTU), and a network center with a database of customers who havepurchased a VLU. The network center interfaces with the NationalCriminal Information Center. The entries of that database comprise theVIN number of the customer's vehicle and an identification code assignedto the customer's VLU.

When a LoJack® product customer reports that her vehicle has beenstolen, the VIN number of the vehicle is reported to a law enforcementcenter for entry into a database of stolen vehicles. The network centerincludes software that interfaces with the database of the lawenforcement center to compare the VIN number of the stolen vehicle withthe database of the network center which includes VIN numberscorresponding to VLU identification codes. When there is a match betweena VIN number of a stolen vehicle and a VLU identification code, as wouldbe the case when the stolen vehicle is equipped with a VLU, and when thecenter has acknowledged the vehicle has been stolen, the network centercommunicates with the RTUs of the various communication towers(currently there are 130 nationwide) and each tower transmits a messageto activate the transponder of the particular VLU bearing theidentification code.

The transponder of the VLU in the stolen vehicle is thus activated andbegins transmitting the unique VLU identification code. The VTU of anylaw enforcement vehicles proximate the stolen vehicle receive this VLUtransponder code and, based on signal strength and directionalinformation, the appropriate law enforcement vehicle can take activesteps to recover the stolen vehicle. See, for example, U.S. Pat. Nos.4,177,466; 4,818,988; 4,908,609; 5,704,008; 5,917,423; 6,229,988;6,522,698; and 6,665,613 all incorporated herein by this reference.

Since the VLU unit is powered by the vehicle's battery, power managementtechniques must be employed in the VLU to ensure the VLU does not drainthe vehicle's battery. One prior technique employed by the applicantincludes programming the VLU to “wake up” and check for messages fromthe communication towers only periodically, e.g., every 8 seconds for0.2 seconds. The timing of the sleep and wake-up modes was synchronizedto the transmission schedule of one communication tower. See U.S. Pat.No. 6,229,988.

But, if the vehicle equipped with the VLU so programmed moves out of thetransmission range of that tower, when the VLU wakes up, no signal willbe received from that tower. According to prior methods, the VLU mustwake up for a longer time in order to be sure to receive a towertransmission since the VLU has no memory of which time slot the tower islikely to transmit. This results in increased power consumption.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a vehiclelocating unit with improved power management technique.

It is a further object of this invention to provide such a vehiclelocating unit whose wake-up and sleep modes are synchronized to thecommunication source transmitting the strongest signal.

It is a further object of this invention to provide such a vehiclelocating unit which continuously updates its memory to store theidentity of one or more communication towers with the strongest signals.

The subject invention results from the realization that a more effectivepower management subsystem for a VLU is configured to alternately entersleep and wake-up modes, to synchronize the wake-up mode to thecommunication source (e.g., tower) transmitting the strongest signal,and to test the signal strength of at least one additional communicationsource in sequence.

The subject invention, however, in other embodiments, need not achieveall these objectives and the claims hereof should not be limited tostructures or methods capable of achieving these objectives.

The subject invention features a vehicle locating unit with improvedpower management. A receiver receives a signal from a network ofcommunication sources and a signal strength monitoring subsystemdetermines which of the communication sources are transmitting thestrongest signals. The power management subsystem is responsive to thesignal strength monitoring subsystem and is configured to: alternativelyenter sleep and wake-up modes, synchronize the wake-up mode to thecommunication source transmitting the strongest signal, and test thesignal strength of at least one additional communication sourceaccording to a predefined sequence.

Typically, the power management subsystem is configured to test andstore the identity of two communication sources with the two strongestsignals, switch to synchronization with any communication source havinga signal stronger than the strongest signal of the two storedcommunication sources, and store the identity of any communicationsource with a signal stronger than the signal of any previously storedcommunication source.

In one embodiment, there are n (e.g., eight) communication sources eachtransmitting a signal at a different time every n seconds. Preferably,the power management system is configured to include a start-up modewherein all communication sources are tested. In one preferredembodiment, the power management subsystem is implemented in amicrocontroller which is configured to power down the receiver duringthe sleep mode and to power up the receiver during the wake-up mode. Oneexample of a signal strength monitoring subsystem includes ademodulation circuit embodied in a transceiver.

A method of checking messages from a network of communication sources inaccordance with this invention includes initially testing the signalstrength of a plurality of communication sources, storing the identityof the communication sources with the two strongest signals,alternatively entering a sleep mode and a wake-up mode, the wake-up modesynchronized to the communication source with the strongest signal,testing the signal strength of one additional communication source,switching synchronization to the additional communication source if saidsource presents a signal stronger than the signal of the storedcommunication source with the strongest signal, and replacing theidentity of any stored communication source if an additionalcommunication source tested in sequence presents a signal stronger thanthe signal of said stored communication source.

For VLUs and other electronic receivers which receive a signal from anetwork of communication sources, a signal strength monitoring subsystemdetermines which of the communication sources are transmitting thestrongest signals. A power management subsystem is responsive to thesignal strength monitoring subsystem and is configured to: alternativelyenter sleep and wake-up modes, synchronize the wake-up mode to thecommunication source transmitting the strongest signal, and test thesignal strength of at least one additional communication source toensure the wake-up mode is synchronized to the communication sourcetransmitting the strongest signal.

One embodiment features a vehicle locating unit power management systemcomprising a memory, and a controller configured to alternatively outputsleep and wake-up mode signals, store in said memory the identity of atleast a first communication source presenting the strongest signal, testthe signal strength of at least one different communication sourceduring the wake-up mode, synchronize the wake-up mode to thecommunication source identified in said memory, and update the memory tostore the identity of a different communication source presenting asignal stronger than the first communication source.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1 is a schematic block diagram showing the primary componentsassociated with a vehicle recovery system in accordance with the subjectinvention;

FIG. 2 is a block diagram showing the primary components associated witha vehicle locating unit in accordance with the subject invention;

FIG. 3 is a flow chart depicting the primary steps associated with oneexample of the programming of the microcontroller of the vehiclelocating unit shown in FIG. 2 as it relates to power management; and

FIG. 4 is a schematic timing diagram showing a time slot synchronizationpattern for an example of a communication network including eightcommunication towers.

DETAILED DESCRIPTION OF THE INVENTION

Aside from the preferred embodiment or embodiments disclosed below, thisinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Thus, it is to be understood that theinvention is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. If only oneembodiment is described herein, the claims hereof are not to be limitedto that embodiment. Moreover, the claims hereof are not to be readrestrictively unless there is clear and convincing evidence manifestinga certain exclusion, restriction, or disclaimer.

As discussed in the background section above, the applicant's successfuland popular vehicle recovery system sold under the trademark LoJack®includes a small electronic vehicle locating unit (VLU) 10, FIG. 1, witha transponder 12 hidden within a vehicle 14, a private network ofcommunication towers 16 each with a remote transmitting unit (RTU) 18,one or more law enforcement vehicles 20 equipped with a vehicle trackingunit (VTU) 22, and network center 24.

When a LoJack® product customer reports that her vehicle has beenstolen, the VIN number of the vehicle is reported to law enforcementcenter 26 for entry into database 28 of stolen vehicles. Network center24 includes software that interfaces with database 28 of law enforcementcenter 26 to compare the VIN number of the stolen vehicle with database30 of network center 24 which includes VIN numbers corresponding to VLUidentification codes. When there is a match between a VIN number of astolen vehicle and a VLU identification code, as would be the case whenstolen vehicle 14 is equipped with VLU 10, network center 24communicates with the RTUs 18 of the various communication towers 16 andeach tower transmits a message to activate transponder 12 of VLU 10bearing the particular identification code.

Transponder 12 of VLU 10 in stolen vehicle 14, once activated, beginstransmitting a unique VLU identification code. VTU 22 of law enforcementvehicle 20 proximate stolen vehicle 14 receives this VLU transpondercode and, based on signal strength and directional information, theappropriate law enforcement vehicle can take active steps to recoverstolen vehicle 14.

VLU 10′, FIG. 2, in accordance with the subject invention includestransceiver 40 or, in another example, a receiver without transmissioncapabilities. Signal strength monitoring subsystem 42, in oneembodiment, is a demodulator circuit on a chip within transceiver 40 andoutputs a signal identifying and characterizing the signal strength ofall signals received by transceiver 40 via antenna 44 from thecommunication network and one or more communication towers 16, FIG. 1.

Microcontroller 46, FIG. 2, (e.g., a Texas Instrument microcontrollermodel No. MSP430) receives the output of subsystem 42, is programmed toevaluate the signal strength of all signals received by transceiver 40,and is also programmed to alternatively cause transceiver 40 to entersleep and wake-up modes to save battery power by outputting a signal topower supply unit circuitry 48 in accordance with the flow-chart of FIG.3. Memory 47, FIG. 2, is shown separate from controller 47 but manymicrocontrollers, as is known by those skilled in the art, have internalmemories including the controller example above.

In the following example, there are eight communication sources orLoJack® towers A-H, FIG. 4, transmitting signals to VLU 10′, FIG. 2.Each transmits a synchronization signal at a different time t₀-t₇ eacheight seconds and possibly a message (in the case of a reportedly stolenvehicle) in which instance microcontroller 46, FIG. 2 would activatetransponder 12.

But, transceiver 40, if continuously left on to check for such amessage, would more quickly drain the battery of the vehicle. Accordingto the subject invention, microcontroller 46 at start-up, step 60, FIG.3, tests the signal strength of towers A-H by analyzing the output ofsignal strength monitoring subsystem 42. In this test mode, the signalstrength of each tower is noted and if any signal carries a message, themessage is acted upon.

The identity of the two strongest tower signals is stored in memory 47,FIG. 2, step 62, FIG. 3, and the wake-up mode is then synchronized, step64, to the strongest of these two signals. Next, the sleep mode isentered and when the wake-up mode is activated in synchronization withthe communication tower presenting the strongest signal, the signalstrength of the two previously stored towers is tested as is the signalstrength of one additional communication tower, in sequence.

As an example, suppose towers A and B, FIG. 4, are transmitting thestrongest signals by virtue of their proximity to VLU 10, FIG. 2. Iftower A's signal is assumed to be stronger than tower B's signal, thewake-up mode synchronization is in accordance with tower A's signal.Thus, in each cycle, (typical wake up times are 8 sec. apart),controller 46 would power up transceiver 40 by signaling power supplyunit circuit 48 at time t₀, FIG. 4, and sleep between times t₁-t₇, steps66-68. At the next wake-up time, the signal strength of the twopreviously stored towers (A and B) is tested for strength as is thesignal strength of the next tower according to a predefined sequencewhich, in this example, is tower C, step 70. In this way, if at any timedue to movement of the vehicle a different tower in the sequence A-Hpresents a stronger signal than a) the tower upon which controller 46synchronizes the wake-up mode or b) the stored identity of the towerwith the second strongest signal, the identity of the new tower isstored in memory 47, FIG. 2, steps 72-74, FIG. 3, and synchronization tothe tower with the strongest signal is ensured at step 64.

Suppose, however, that tower C does not present a stronger signal thaneither towers A or B and that the wake up and sleep modes are stillsynchronized to tower A in step 66. At steps 68 and 70 towers A, B, andnow D are tested and if tower D's signal strength is not stronger thaneither tower A or B and once again the sleep mode is entered, step 66.Upon entering the wake-up mode at step 68, still synchronized to towerA, the signal strength of towers A, B, and now E is checked, step 70.

Now, if the signal strength of tower E is stronger than the signalstrength of tower B, but not tower A, the identity of tower E is storedin memory 47, FIG. 2 at step 74, FIG. 3, replacing tower B. But at step64 the wake-up mode is still synchronized to the strongest tower, namelytower A at steps 64-68.

So, next, the signal strengths of towers A, E, and F are tested, step70; and suppose at step 72 the signal strength of tower F is strongerthan tower A and E but tower A is still stronger than tower E. Now,synchronization will be according to tower F at step 64 and at step 70,towers F, A, and G are tested, and so on.

In another example, imagine towers C and D initially present thestrongest first and second signals to the VLU. The wake up mode isinitially synchronized to tower C and the identity of towers C and D arestored in memory. After the first sleep mode, the signal strength oftowers C, D, and E are tested, and next towers C, D, and F, and thentowers C, D, and G, and then towers C, D, and H, and so on—oneadditional tower during each subsequent wake-up mode. If during thiswake-up/sleep mode cycle, towers C and D remain the strongest twotowers, synchronization remains with tower C and the memory continues tostore the identity of towers C and D. If during the next cycle, whentower A is tested and is found to present a signal stronger than tower Dbut not C, the memory is updated to store the identity of towers C andA, synchronization continues according to tower C's transmissionschedule, and during each subsequent wake-up mode the signal strength oftowers C, A, and B; C, A, and D; C, A, and E; C, A, and F . . . and soon is tested.

In this way, the identity of the towers which transmit the two strongestsignals is always stored and controller 46, FIG. 2 in sequence checksanother tower in the wake-up mode to maintain in storage 47, FIG. 2, theidentity of the two towers emitting the strongest signals. Also,controller 46 ensures the wake-up mode is synchronized to only the toweremitting the strongest signal. Power is conserved but now in a way whichensures no communication message from any tower in the network ismissed. To enter the sleep mode, microcontroller 46 sends a signal topower supply unit 48 which then powers down transceiver 40. To enter thewake-up mode, microcontroller 46 sends a signal to power supply unit 48which then again provides power to transceiver 40 so that it can receivesignals via antenna 44.

The example presented above in reference to FIGS. 3-4 assumes eighttowers in a given region, continuous storage of the two strongest towersignals, and testing of an additional tower in a specific sequence, butthis is an example only and not a limitation of the subject invention:any number and combination of towers and storage of tower combinationscan be used. The example above also assumes that the power managementmethod of the subject invention applies to a VLU of a vehicle recoverysystem but the invention hereof may find applicability to batterypowered electronic devices other than VLUs.

Thus, although specific features of the invention are shown in somedrawings and not in others, this is for convenience only as each featuremay be combined with any or all of the other features in accordance withthe invention. Moreover, the words “including”, “comprising”, “having”,and “with” as used herein are to be interpreted broadly andcomprehensively and are not limited to any physical interconnection.Also, any embodiments disclosed in the subject application are not to betaken as the only possible embodiments. Other embodiments will occur tothose skilled in the art and are within the following claims.

In addition, any amendment presented during the prosecution of thepatent application for this patent is not a disclaimer of any claimelement presented in the application as filed: those skilled in the artcannot reasonably be expected to draft a claim that would literallyencompass all possible equivalents, many equivalents will beunforeseeable at the time of the amendment and are beyond a fairinterpretation of what is to be surrendered (if anything), the rationaleunderlying the amendment may bear no more than a tangential relation tomany equivalents, and/or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for anyclaim element amended.

1. A method of checking messages from a network of communicationsources, the method comprising: initially testing the signal strength ofa plurality of communication sources; storing the identity of thecommunication sources with the two strongest signals; alternativelyentering a sleep mode and a wake-up mode, the wake-up mode synchronizedto the communication source with the strongest signal; testing thesignal strength of one additional communication source; switchingsynchronization to the additional communication source if said sourcepresents a signal stronger than the signal of a stored communicationsource with the strongest signal; and replacing the identity of anystored communication source if an additional communication source testedin sequence presents a signal stronger than the signal of said storedcommunication source.
 2. The method of claim 1 in which there are ncommunication sources each transmitting a signal at a different timeevery n seconds.
 3. The method of claim 2 in which n is
 8. 4. The methodof claim 1 including all communication sources in a start-up mode. 5.The method of claim 1 including powering down during the sleep mode andpowering up during the wake-up mode.
 6. The method of claim 1 in whichthe checking of messages from a network of communication sourcesincludes improving power management.